Thin dual-aperture zoom digital camera

ABSTRACT

A dual-aperture zoom camera comprising a Wide camera with a respective Wide lens and a Tele camera with a respective Tele lens, the Wide and Tele cameras mounted directly on a single printed circuit board, wherein the Wide and Tele lenses have respective effective focal lengths EFL W  and EFL T  and respective total track lengths TTL W  and TTL T  and wherein TTL W /EFL W &gt;1.1 and TTL T /EFL T &lt;1.0. Optionally, the dual-aperture zoom camera may further comprise an optical OIS controller configured to provide a compensation lens movement according to a user-defined zoom factor (ZF) and a camera tilt (CT) through LMV=CT*EFL ZF , where EFL ZF  is a zoom-factor dependent effective focal length.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority from U.S. ProvisionalPatent Application No. 61/842,987 titled “Miniature telephoto lensassembly” and filed Jul. 4, 2013, which is incorporated herein byreference in its entirety.

FIELD

Embodiments disclosed herein relate in general to digital cameras, andmore particularly, to thin dual-aperture zoom digital cameras that canbe incorporated in a portable electronic product such as a mobile phone.

BACKGROUND

Compact multi-aperture and in particular dual-aperture (also referred toas “dual-lens” or “dual-camera”) digital cameras are known.Miniaturization technologies allow incorporation of such cameras incompact portable electronic devices such as tablets and mobile phones(the latter referred to hereinafter generically as “smartphones”), wherethey provide advanced imaging capabilities such as zoom, see e.g.co-owned PCT patent application No. PCT/IB2013/060356 titled“High-resolution thin multi-aperture imaging systems”, which isincorporated herein by reference in its entirety. A two-camera system(exemplarily including a wide-angle (or “Wide”) camera and a telephoto(or “Tele”) camera) is calibrated in an end product (e.g. in asmartphone) after manufacturing.

System calibration matches Tele and Wide image pixels by capturing inboth cameras known objects. This enables faster and more reliableapplication of fusion between the two cameras, as described inPCT/IB2013/060356. One problem with such cameras may arise from mishapssuch as drop impact. The latter may cause a relative movement betweenthe two cameras after system calibration, changing the pixel matchingbetween Tele and Wide images and thus preventing fast reliable fusion ofthe Tele and Wide images.

Another problem with dual-aperture zoom cameras relates to their height.There is a large difference in the height (also known as total tracklength or “TTL”) of the Tele and Wide cameras. The TTL, see FIG. 1, isdefined as the maximal distance between the object-side surface of afirst lens element and a camera image sensor plane. In the following,“W” and “T” subscripts refer respectively to Wide and Tele cameras. Inmost miniature lenses, the TTL is larger than the lens effective focallength (EFL), which has a meaning well known in the art, see FIG. 1. Atypical TTL/EFL ratio for a given lens (or lens assembly) is around 1.3.In a single-aperture smartphone camera, EFL is typically 3.5 mm, leadingto a field of view of 70-80°. Assuming one wishes to achieve adual-aperture X2 optical zoom in a smartphone, it would be natural touse EFL_(W)=3.5 mm and EFL=2×EFL_(W) =7 mm. However, without spatialrestrictions, the Wide lens will have an EFL_(W)=3.5 mm and a TTL_(W) of3.5×1.3=4.55 mm, while the Tele lens will have EFL=7 mm and TTL_(T) of7×1.3=9.1 mm. The incorporation of a 9.1 mm lens in a smartphone camerawould lead to a camera height of around 9.8 mm, which is unacceptablefor many smartphone makers. Also the large height difference (approx.4.55 mm) between the Wide and Tele cameras can cause shadowing andlight-blocking problems, see FIG. 2.

A third problem relates to the implementation of standard optical imagestabilization (OIS) in a dual-aperture zoom camera. Standard OIScompensates for camera tilt (“CT”) by a parallel-to-the image sensor(exemplarily in the X-Y plane) lens movement (“LMV”). Camera tilt causesimage blur. The amount of LMV (in mm) needed to counter a given cameratilt depends on the cameras lens EFL, according to the relationLMV=CT*EFL where “CT” is in radians and EFL is in mm. Since as shownabove a dual-aperture zoom camera may include two lenses withsignificantly different EFLs, it is impossible to move both lensestogether and achieve optimal tilt compensation for both Tele and Widecameras. That is, since the tilt is the same for both cameras, amovement that will cancel the tilt for the Wide camera will beinsufficient to cancel the tilt for the Tele camera. Similarly, amovement that will cancel the tilt for the Tele camera willover-compensate the tilt cancellation for the Wide camera. Assigning aseparate OIS actuator to each camera can achieve simultaneous tiltcompensation, but at the expense of a complicated and expensive camerasystem.

SUMMARY

Embodiments disclosed herein refer to thin dual-aperture zoom cameraswith improved drop impact resistance, smaller total thickness, smallerTTL difference between Wide and Tele cameras and improved OIScompensation.

In some embodiments there are provided dual-aperture zoom camerascomprising a Wide camera with a respective Wide lens and a Tele camerawith a respective Tele lens, the Wide and Tele cameras mounted directlyon a single printed circuit board, wherein the Wide and Tele lenses haverespective effective focal lengths EFL_(W) and EFL_(T) and respectivetotal track lengths TTL_(W) and TTL_(T) and wherein TTL_(W)/EFL_(W)>1.1and TTL_(T)/EFL_(T)<1.0.

In some embodiments, a dual-aperture zoom camera disclosed hereinfurther comprises an OIS controller configured to provide a compensationlens movement according to a camera tilt input and a user-defined zoomfactor through LMV=CT*EFL_(ZF), wherein EFL_(ZF) is a “zoom-factordependent EFL”.

In some embodiments, the Tele lens is a lens as described in detail inU.S. provisional patent application No. 61/842,987 and in U.S. patentapplication Ser. No. 14/367,924, titled “Miniature telephoto lensassembly”, both of which are incorporated herein by reference in theirentirety.

In some embodiments there are provided methods for manufacturing adual-aperture zoom camera comprising the steps of providing a Widecamera having a Wide lens with an effective focal length EFL_(W) and atotal track length TTL_(W), providing a Tele camera having a Tele lenswith an effective focal length EFL_(T) and a total track length TTL_(T),wherein TTL_(W)/EFL_(W)>1.1 and wherein TTL_(T)/EFL_(T)<1.0, andmounting the Wide and Tele cameras directly on a single printed circuitboard.

In some embodiments, the methods further comprise the step ofconfiguring an OIS controller of the dual-aperture zoom camera tocompensate lens movement of the Wide and Tele lenses according to acamera tilt input and a user-defined zoom factor.

BRIE DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments are herein described, by way of example only,with reference to the accompanying drawings, wherein:

FIG. 1 shows definitions of TTL and EFL;

FIG. 2 shows shadowing and light-blocking problems caused by heightdifferences between Wide and Tele cameras in a dual-aperture camera;

FIG. 3 shows an embodiment of a dual-aperture camera disclosed herein;

FIG. 4 shows schematically in a block diagram details of the cameraembodiment of FIG. 3.

DETAILED DESCRIPTION

The present inventors have determined that camera movement (due toexemplarily, but not limited to mishaps such as drop impact) can beavoided or minimized by mounting the two cameras directly on a singleprinted circuit board and by minimizing a distance “d” therebetween.FIG. 3 shows an embodiment of a dual-aperture camera 300 that includestwo cameras 302 and 304 mounted directly on a single printed circuitboard 306. Each camera includes a lens assembly (respectively 306 and308), an actuator (respectively 310 and 312) and an image sensor(respectively 314 and 316). The two actuators are rigidly mounted on arigid base 318 that is flexibly connected to the printed board throughflexible elements 320. Base 318 is movable by an OIS mechanism (notshown) controlled by an OIS controller 402 (FIG. 4). The OIS controlleris coupled to, and receives camera tilt information from, a tilt sensor(exemplarily a gyroscope) 404 (FIG. 4). More details of an exemplary OISprocedure as disclosed herein are given below with reference to FIG. 4.The two cameras are separated by a small distance “d”, typically 1 mm.This small distance between cameras also reduces the perspective effect,enabling smoother zoom transition between cameras. In some embodimentsand optionally, a magnetic shield plate as described in co-owned U.S.patent application Ser. No. 14/365,718 titled “Magnetic shieldingbetween voice coil motors in a dual-aperture camera”, which isincorporated herein by reference in its entirety, may be inserted in thegap with width d between the Wide and Tele cameras.

In general, camera dimensions shown in FIG. 3 may be as follows: alength L of the camera (in the Y direction) may vary between 13-25 mm, awidth W of the camera (in the X direction) may vary between 6-12 mm, anda height H of the camera (in the Z direction, perpendicular to the X-Yplane) may vary between 4-12 mm. More typically in a smartphone cameradisclosed herein, L=18 mm, W=8.5 mm and H=7 mm.

The present inventors have further determined that in some embodiments,the problem posed by the large difference in the TTL/EFL ratio of knowndual-aperture camera Tele and Wide lenses may be solved through use of astandard lens for the Wide camera (TTL_(W)/EFL_(W)>1.1, typically 1.3)and of a special Tele lens design for the Tele camera(TTL_(T)/EFL_(T)<1, typically 0.87). Exemplarily, the special Tele lensdesign may be as described in co-owned and U.S. patent application Ser.No. 14/367,924, titled “Miniature telephoto lens assembly”, which isincorporated herein by reference in its entirety. A Tele lens assemblydescribed in detail therein comprises five lenses that include, in orderfrom an object side to an image side: a first lens element with positiverefractive power having a convex object-side surface, a second lenselement with negative refractive power having a thickness d₂ on anoptical axis and separated from the first lens element by a first airgap, a third lens element with negative refractive power and separatedfrom the second lens element by a second air gap, a fourth lens elementhaving a positive refractive power and separated from the third lenselement by a third air gap, and a fifth lens element having a negativerefractive power, separated from the fourth lens element by a fourth airgap, the fifth lens element having a thickness d₅ on the optical axis.The lens assembly may exemplarily have an F number (F#) <3.2. In anembodiment, the focal length of the first lens element f1 is smallerthan TTL_(T)/2, the first, third and fifth lens elements have each anAbbe number greater than 50, the second and fourth lens elements haveeach an Abbe number smaller than 30, the first air gap is smaller thand₂/2, the third air gap is greater than TTL_(T)/5 and the fourth air gapis smaller than 1.5d₅. In some embodiments, the surfaces of the lenselements may be aspheric.

Using a Tele lens designed as above, TTL_(T) is reduced to 7×0.87=6.09mm, leading to a camera height of less than 7 mm (acceptable in asmartphone). The height difference (vs. the Wide camera) is also reducedto approx. 1.65 mm, causing less shadowing and light blocking problems.

In some embodiments of a dual-aperture camera disclosed herein, theratio “e”=EFL_(T)/EFL_(W) is in the range 1.3-2.0. In some embodiments,the ratio TTL_(T)/TTL_(W)<0.8e. In some embodiments, TTL_(T)/TTL_(W) isin the range 1.0-1.25. In general, in camera embodiments disclosedherein, EFL_(W) may be in the range 2.5-6 mm and EFL_(T) may be in therange 5-12 mm.

With reference now to FIG. 4, in operation, tilt sensor 404 dynamicallymeasures the camera tilt (which is the same for both the Wide and Telecameras). OIS controller 402, which is coupled to the actuators of bothcameras through base 318, receives a CT input from the tilt sensor and auser-defined zoom factor, and controls the lens movement of the twocameras to compensate for the tilt. The LMV is exemplarily in the X-Yplane. The OIS controller is configured to provide a LMV equal toCT*EFL_(ZF), where “EFL_(ZF)” is chosen according to the user-definedZF. In an exemplary OIS procedure, when ZF=1, LMV is determined by theWide camera EFL_(W) (i.e. EFL_(ZF)=EFL_(W) and LMV=CT*EFL_(W)). Furtherexemplarily, when ZF>e (i.e. ZF>EFL_(T)/EFL_(W)), LMV is determined byEFL_(T) (i.e. EFL_(ZF) =EFL_(T) and LMV=CT* EFL_(T)). Furtherexemplarily yet, for a ZF between 1 and e, the EFL_(ZF) may shiftgradually from EFL_(W) to EFL_(T) according to EFL_(ZF)=ZF*EFL_(W). Asmentioned, the OIS procedure above is exemplary, and other OISprocedures may use other relationships between EFL_(ZF) and ZF toprovide other type of LMV.

While this disclosure has been described in terms of certain embodimentsand generally associated methods, alterations and permutations of theembodiments and methods will be apparent to those skilled in the art.The disclosure is to be understood as not limited by the specificembodiments described herein, but only by the scope of the appendedclaims.

1. A dual-aperture zoom camera, comprising a Wide camera with arespective Wide lens and a Tele camera with a respective Tele lens, theWide and Tele cameras mounted directly on a single printed circuitboard, wherein the Wide and Tele lenses have respective effective focallengths EFL_(W) and EFL_(T) and respective total track lengths TTL_(W)and TTL_(T), and wherein TTL_(W)/EFL_(W)>1.1 and TTL_(T)/EFL_(T)<1.0. 2.The dual-aperture zoom camera of claim 1 wherein EFL_(T)/EFL_(W)=e andfurther comprising an optical image stabilization (OIS) mechanismconfigured to provide a compensation lens movement (LMV) according to acamera tilt (CT) input and a user-defined zoom factor (ZF) throughLMV=CT*EFL_(ZF), wherein CT is a camera tilt in radians and EFL_(ZF) isa zoom-factor dependent effective focal length in millimeters.
 3. Thedual-aperture zoom camera of claim 2, wherein for ZF=1,EFL_(ZF)=EFL_(W).
 4. The dual-aperture zoom camera of claim 2, whereinfor ZF=e, EFL_(ZF)=EFL_(T).
 5. The dual-aperture zoom camera of claim 2,wherein for a ZF in the range 1<ZF<e, EFL_(ZF)=ZF*EFL_(W).
 6. Thedual-aperture zoom camera of claim 2, wherein for a ZF in the range1<ZF<e, EFL_(ZF)=EFL_(W).
 7. The dual-aperture zoom camera of claim 2,wherein for a ZF in the range ZF>e, EFL_(ZF)=EFL_(T).
 8. Thedual-aperture zoom camera of claim 1, wherein a ratio EFL_(T)/EFL_(W) isin the range 1.3-2.5.
 9. The dual-aperture zoom camera of claim 1,wherein a ratio TTL_(T)/TTL_(W) is in the range 1.0-1.25.
 10. Thedual-aperture zoom camera of claim 1, wherein a ratio TTL_(T)/TTL_(W) issmaller that 0.8*(EFL_(T)/EFL_(W)).
 11. The dual-aperture zoom camera ofclaim 1, wherein d is about 1 mm.
 12. (canceled)
 13. (canceled)
 14. Thedual-aperture zoom camera of claim 1, wherein the Tele lens comprises afirst lens element with positive refractive power having a convexobject-side surface, a second lens element with negative refractivepower having a thickness d₂ on an optical axis and separated from thefirst lens element by a first air gap, a third lens element withnegative refractive power and separated from the second lens element bya second air gap, a fourth lens element having a positive refractivepower and separated from the third lens element by a third air gap, anda fifth lens element having a negative refractive power, separated fromthe fourth lens element by a fourth air gap, the fifth lens elementhaving a thickness d₅ on the optical axis.
 15. The dual-aperture zoomcamera of claim 14, wherein the focal length of the first lens elementf1 is smaller than TTL_(T)/2, the first, third and fifth lens elementshave each an Abbe number greater than 50, the second and fourth lenselements have each an Abbe number smaller than 30, the first air gap issmaller than d₂/2, the third air gap is greater than TTL_(T)/5 and thefourth air gap is smaller than 1.5d₅.
 16. A method for manufacturing adual-aperture zoom camera comprising the steps of: a) providing a Widecamera having a Wide lens with an effective focal length (EFL) EFL_(W)and a total track length (TTL) TTL_(W); b) providing a Tele camerahaving a Tele lens with an effective focal length EFL_(T) and a totaltrack length TTL_(T), wherein TTL_(W)/EFL_(W)>1.1 and whereinTTL_(T)/EFL_(T)<1.0; and c) mounting the Wide and Tele cameras directlyon a single printed circuit board.
 17. The method of claim 16, furthercomprising the step of: d) configuring an optical image stabilization(OIS) controller of the dual-aperture zoom camera to compensate lensmovement (LMV) of the Wide and Tele lenses according to a camera tilt(CT) input and a user-defined zoom factor (ZF).
 18. The method of claim16, wherein the step of mounting includes spacing the Wide and Telecameras on the board such that a distance d therebetween is about 1 mm.19. The method of claim 17, wherein EFL_(T)/EFL_(W)=e, whereinLMV=CT*EFL_(ZF) and wherein CT is a camera tilt in radians and EFL_(ZF)is a zoom-factor dependent effective focal length in millimeters. 20.The method of claim 19, wherein for ZF=1, EFL_(ZF)=EFL_(W).
 21. Themethod of claim 19, wherein for ZF=e, EFL_(ZF)=EFL_(T).
 22. The methodof claim 19, wherein for a ZF in the range 1<ZF<e, EFL_(ZF)=ZF*EFL_(W).23. (canceled)
 24. (canceled)
 25. (canceled)
 26. (canceled)
 27. Themethod of claim 17, wherein a ratio TTL_(T)/TTL_(W) is smaller that0.8*(EFL_(T)/EFL_(W)).
 28. The method of claim 16, wherein the step ofproviding a Tele camera having a Tele lens with an effective focallength EFL_(T) and a total track length TTL_(T) includes providing aTele lens comprising a first lens element with positive refractive powerhaving a convex object-side surface, a second lens element with negativerefractive power having a thickness d₂ on an optical axis and separatedfrom the first lens element by a first air gap, a third lens elementwith negative refractive power and separated from the second lenselement by a second air gap, a fourth lens element having a positiverefractive power and separated from the third lens element by a thirdair gap, and a fifth lens element having a negative refractive power,separated from the fourth lens element by a fourth air gap, the fifthlens element having a thickness d₅ on the optical axis.
 29. The methodof claim 28, wherein the focal length of the first lens element f1 issmaller than TTL_(T)/2, the first, third and fifth lens elements haveeach an Abbe number greater than 50, the second and fourth lens elementshave each an Abbe number smaller than 30, the first air gap is smallerthan d₂/2, the third air gap is greater than TTL_(T)/5 and the fourthair gap is smaller than 1.5d₅.